Try on the jeans and mark the desired length with pins or chalk
Measure how much length needs to be removed
Turn the jeans inside out
Fold the excess fabric up to the inside at the marked line
Keep the original hem at the bottom edge
Pin the fold in place all the way around each leg
Sew a straight stitch close to the original hem, catching the folded fabric
Trim any extra fabric if needed, leaving a small seam allowance
Press the hem flat with an iron
Turn the jeans right side out and check the length
Repeat on the other leg, matching both hems evenly