We have the answer to your question in the whole passage that those verses are found in, so I will quote verses 1-9: “Now the whole earth had one language and one speech. And it came to pass, as they journeyed from the east, that they found a plain in the land of Shinar, and they dwelt there. Then they said to one another, ‘Come, LET US make bricks and bake them thoroughly.’ They had brick for stone, and they had asphalt for mortar. And they said, ‘Come, LET US build ourselves a city, and a tower whose top is in the heavens; LET US make a name for OURSELVES, lest we be scattered abroad over the face of the whole earth.’ But THE LORD CAME DOWN to see the city and the tower which THE SONS OF MEN had built. And the LORD said, ‘Indeed the people are one and they all have one language, and this is what they begin to do; now nothing that they propose to do will be withheld from them. Come LET US go down and there confuse their language, that they may not understand one another’s speech.’ So THE LORD SCATTERED THEM abroad from there over the face of all the earth, and they ceased building the city. There for the name is called Babel, because there THE LORD CONFUSED THE LANGUAGE of all the earth; and from there THE LORD SCATTERED THEM abroad over the fact of all the earth.”

I have capitalized the words that help to answer your question. In verses 3-4 we have the words “let us” referring to “the sons of men” who built the city and the tower. In verse 5 we see that “the LORD came down” so we know that refers to God. Then in verse 7 God says, “let US go down and there confuse their language” followed by verses 8 & 9 where we are told “So the LORD scattered them” and “the LORD confused the language of all the earth.” There are only two groups involved here: the “sons of men” and the “LORD” (God). We know that the “sons of men” were talking among themselves, so we conclude that when God says “let US,” one of the Persons of the holy Trinity is talking to the other two Persons of the Trinity. When we use the word Trinity, we are expressing the belief that “God is One God who at the same time subsists in three Persons; the Father, the Son, and the Holy Spirit.”

I would like to take us back to Genesis Chapter One. On the sixth day of creation, we read in verses 26-27, “Then God said, “Let Us make man in Our image, according to Our likeness…So God created man in His own image.” Here too we see God talking and using the same words “let Us” as He does in Genesis 11:7. He also uses the words “Our image” and “Our likeness.” These words teach us clearly that God is a “plurality” (made up of at least 2 Persons) and in the New Testament the Lord Jesus taught us clearly that God is THREE PERSONS. I am referring to Matthew 28:19 where Jesus said, “Go therefore and make disciples of all the nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit.” Here we see THREE PERSONS and yet they are ONE GOD! We can’t be sure which Person was speaking to the other two in Genesis 1:26-27 and 11:7, but we can, by faith, accept this wonderful truth that these THREE are ONE GOD who have the same attributes of being Omnipotent (all-powerful), Omniscient (all-knowing), and Omnipresent (present everywhere), and that they have fellowship with each other (by speaking to one another).

You may be thinking, “What did God mean when He said, “Let Us make man in our image?” He could not have meant “Let us make man to share our Divine attributes,” for then we too would be “just like God.” One suggestion is given by William MacDonald, and I will close with that. He says, “Man was placed on earth as God’s representative, and that He resembles God in certain ways. Just as God is a Trinity (Father, Son, and Holy Spirit), so man is a tripartite being (spirit, soul, and body). Like God, man has intellect, a moral nature, the power to communicate with others, and an emotional nature that transcends instinct. There is no thought of physical likeness here.”  (DO)  (701.1)