457 Direct Rollover from Empower to Vanguard Roth IRA

My husband did a direct rollover from a 457 in Empower to a Vanguard Roth IRA.   We have confirmed that the 457 was pre-tax so we should have paid taxes on this amount.   We received two 1099-R forms, one from Empower and one from Vanguard.  From Empower, the taxable amount was zero and Box #7 distribution code is G.  For Vanguard, the taxable amount equals the gross distribution amount from Box #1 and Box #7 distribution code was 7.  How can I amend my tax return in Turbotax so we correctly pay the taxes that are due.