You'll need to contact the issuer of Form 1099-G -- probably the DC Department of Employment Services, if the form reflects unemployment -- to get the information.
The ID number may be the same as the Payer's TIN in the upper left of the return, but you need to make sure.
You indicate that you had state taxes withheld, so you apparently have an amount on line 11 (State income tax withheld). If that's the case, TurboTax will require an entry in line 10b.
