input it as is with the code g then go down to the bottom of the 1099-R input screen and check off the box for a full rollover to a Roth. WHO gave them the advice to convert $250K in one shot to a Roth? Too late now but I would have rolled to a Traditional IRA first - then done a series of Roth conversion watching income limits and brackets. That's a lot of taxes owed on this one. 

It wasn't a roth 401K to a roth ira was it? then the g makes sense.