I have two User names on my Mac - both are me but I can only access one of them - Mac OS Big Sur 11.7.10

Thanks for replying to my post! No, Disk Utility shows Macintosh HD and Macintosh - Data volumes. I must admit that I don't know how the APFS filesystem works but I think that the initial problem was caused by my using the Migration Assistant at some stage when I moved to a new computer (the MacBook Pro) - because I had Tricia as my User name on my previous computer I vaguely remember some message about having to use a different User name, hence Tricia 1. While I've been trying to free up space on my computer I deleted my husband's account (not that it freed up very much space at all), however System Settings User and Group preferences list only my full name as Admin and Guest. Nothing else. My problem continues to be that there is no way I can gain access to the Tricia 1 account. I have found a couple of other posts in the forums of people who've had similar problems - also due to Migration Assistant, it would seem - however, the answers seem to be that there is no way that the two users can be merged and it appears the only solution is that one user must be deleted. I wouldn't mind deleting the Tricia account (26 GB) if I could actually access the Tricia 1 account but I simply haven't been able to find a way to log in to Tricia 1. Any ideas about that? Thank you again for taking the rime to reply.

Thank you for your suggestion. I've heard of CCC - but years ago now - I think it was long before Time Machine and I used a different program from CCC to backup because CCC didn't make a bootable copy - but maybe I'm. wrong. I will download it and give it a try. I'm just wondering whether I would be accessing the data to copy in Finder through the User/Library (that may not be the correct terminology) as I can only login to the Tricia account or perhaps using CCC means that it doesn't matter how I login? Thank you again for your helpful suggestion.