Chances are you wont need the bios update, the Asrock web page indicated that for the FX-6100 requires the bios version 1.10 which is quite old (6 months ago) and was the first official update to the bios. Right now the newest bios update is 1.60 so compared to the 1.10 you should be fine considering you just bought the motherboard recently.
Anyways apart from that, did you go ahead and buy this build without asking for any recommendations? Kind of lost money and value when you went for the FX-6100. There are better processors on the same AM3/AM3+ platform that costs cheaper yet performs better.