There's no real form, but a Motion for Modification of Sentence typically looks like this:
Defendant respectfully XXXXX XXXXX Court
for a modification of sentence, and in support thereof, states:
1. Reasons for the modification (school/job)
2. Reasons for the modification (no longer live in the city, etc)
(as many numbered paragraphs are needed to state the basis for the request)
Wherefore, Defendant respectfully requests [extension for ___]; in the alternative, Defendant respectfully XXXXX XXXXX the house arrest be transferred to _______ in [city], located in Marion County, Indiana.
Send a copy to the court as well as the district attorney who handled your case, and put a note that you have served the State with the copy at the end of the motion.