Custom Variable Lengths Where Stored?

I can’t for the life of me find where the lengths of the textfields for custom fields are stored. I’ve got a bunch of custom textfields with lengths 255 that I want to edit the _cstm table and edit the field lengths in bulk and then update them in the CRM but I can’t find the file to edit in the CRM.

Ugh, I forgot, they are all individual PHP files.