Update Record in Custom API?

Hello, I've tied MS Forms to Power Automate to create a new vendor record in BC when a new vendor fills out the form.  However, the action 'Create Record (V2)' in Power Automate only allows access to 20 pre-selected fields from the vendor table.  I want access to all, so I created an API 'VendorsSOD' and was hoping I could use 'Update Record V3' to use that API to get access to populate the fields I can't get to in 'Create Record V2'.  Is this possible?  I also do not know where to find the Row ID for VendorsSOD.  I thought it would be in the url within SOD but I receive 'not found' errors when trying to insert those into the Row ID field from Power Automate.  I can see the data in VendorsSOD after watching your videos, but not sure I can use it to write back into BC. I appreciate any help, A Lowly Accountant trying to act like a Programmer.