I-485 for my wife and her 2 kids

[triffides]

Hello

Im trying to apply for I-485 for my wife and her 2 kids one is 16 and the other 10 which enter the us truth a wt visa and wanted to know if i have to file separatly for the 3 of them and how much could it bee in fees if i do also which other forms would I need to file.

I will really apriciate an answer ASP
Thank you