Use Conditional Formatting or Formulas to Identify Invoices not formatted properly

Hi All - New to the thread. I have a data set (image below) and I'm hoping to find a way either through a formula or conditional formatting to identify lines not following our invoice number convention (USINV-######) and requiring massaging prior to upload.

InvoiceNumbers.JPG

as a way custom format "USINV-"000000

Or using Cf, use a formula
=LEFT(F2,6)<>"USINV-"

This almost gets me there... is the way to augment this to also validate the right six characters are a six digit number string??

how about
=AND(LEN(F2)<>12,OR(LEFT(F2,6)<>"USINV-",ISNUMBER(RIGHT(F2,6)*1)))

This seems to do the trick! Have a new added wrinkle where an invoice formatted "FINV########" is acceptable too. How can I modify the formula to accommodate this??

Maybe
=OR(AND(LEFT(F2,4)<>"FINV",LEFT(F2,6)<>"USINV-"),NOT(ISNUMBER(RIGHT(F2,6)*1)),LEN(F2)<>12)