Can’t create a computer account with my Apple ID on new MacBook

I just got a MacBook Pro 2020. Tried transferring my data from my old 2015 MacBook with Migration Assistant but that was taking forever, so I opted to log in with my Apple ID on the new Mac, then transfer my files manually. The problem is after logging in with my Apple ID, I’m unable to get past the Create A Computer Account stage. I keep getting a prompt that my name has been taken and “1” is automatically affixed to the end of my account name from my old Mac. And keeps reverting when I try to take it out.