We always here would you like paper or plastic at the market?
Well in building terms this can be a whole diferent senario.
Minconst made a good point about where the vapor barrier goes, (Welcome buy the way!) and I would like to elaborate a bit further because it will help you live healthier.
When you insulate the basement the best method is to use styrofoam insulation,as mentioned.Because it can hold no moisture.Fiberglass insulation uses trapped air to form the thermal barrier which can also trap moisture and mold.I assume you wanted to use foam for this reason.
Now getting to my point,if anyone uses fiberglass for the insulation ALWAYS use kraft faced paper not plastic for a barrier.
The plastic when used in the basement WILL trap the moisture in the fiberglass insulation. Paper actually absorbs some of the moisture and releases or lets it pass through and trys not to keep it.Therfore it is a smart vapor barrier. Foam does not need any barrier however if you can adhere the foam to the backside of the wall and leave the airspace, that would be best.
Always put a dehumidifier in your finished basement.