The answer for this is:

EXEC sp_executesql @sqlToExec, N'@ordernumber MSS_MC1_LookUpIds READONLY, @permmasterlistid MSS_MC1_LookUpIds READONLY, @externalordernumber MSS_MC1_LookUpIds READONLY',

@ordernumber, @permmasterlistid, @externalordernumber

Thank you very much for the response and the links. They really helped me but I have one more question now.

I am using multiple TVPs in my stored procedure and...

If we have multiple parameters in one stored procedure and if any of those parameters has value empty, we should not us skip using a condition related to that parameter...