Hmm, with the size of your board, a free host might not be the best idea. I don't know who might be able to help with hosting, though, but I can help with the conversion.
First step would be to download and extract the converters. Then, you should consult the Instructions.txt file in the Proboards folder. If you have any questions, don't hesitate to ask!
Need a conversion from another forum, but they won't give you the database? Try a crawler converter
. If your converter isn't listed, feel free to post in that thread to ask for one.