Computer lightroom classic migration organization questions

Desperate help is needed. I cannot thank you enough in advance. Here is my issue.

• I started using lightroom on computer A in around 2015 or so. I got a new computer and transferred ComA's catalogs to Computer B in 2018ish.
• In setting up computer B, I could never get the Lightroom catalogs to merge or work correctly. So I started yet another catalog. So now it's 2022, and I have computer C! I want to set this one up correctly.   
  • Note pictures were on my hard drive -- also - thinking about moving pictures to a cloud base, so files don't take up space on my computer.  
• So what do I do? 
  •  A)  Fix the catalog on Computer B (correcting catalogs from ComA) BEFORE migrating to Computer C?
  • B)  Move all to Computer C and then reorganize tags, etc.  

Oh, Yodas of Lightroom - I am willing to do whatever is needed. I have done some reading and see much about how to transfer to a new computer -- but not about fixing errors and changing directories. I can't wait to see what I need to do. I am sorry if this issue has been previously answered. I did look but have been unable to find an answer.   Thank you in advance for your help.