How long can my boyfriend get in jail?

My boyfriend just turned 18 in April. When he was bout 16 or 17 he got charged for burglary and grand theft auto. And was put on jubenile probation. About two days ago he was taken to jail on a burglary and theft charge. He stole the total of $358, an iPod touch, & a bracelet. How long could he get in jail for these charges on account of his earlier charges as a juvenile?