3GP converter .. i think?

i have a verizon Lg the new one that has the 2 speakers on side and an antenna like 7600 or something. Well when i make a video it says that it is an 3gp i think... i need a free converter like 3gp i think or like 3g or g3 something like that and i need it to convert to wmp or something that window movie maker can read.