A locksmith will most likely get you into the car’s main cabin, from where you’ll be able to open the trunk.
Otherwise, you can try and get the trunk open yourself. You can try and use a slim jim, which is a special tool that can help you open car doors.
Push the slim jim into the space between the window and the door, then feel around for a rod. Once you feel it, yank the rod up to unlock the door. Once inside the car, you can unlock the trunk.