The easiest thing to do would be to buy a bolt-on skewer. It will go through the hollow axle on your hub, but instead of having a QR cam, it's got a hex head.
Alternatively, you can replace the axle. That involves buying a solid axle and tracknuts that are threaded the same, removing the guts of the hub (axle, locknuts, cones, spacers, bearings) and putting them back together on the new axle. If you've never rebuilt a hub before, this can be a challenge, or difficult to do correctly.
Alternatively you can just keep the QR. I like riding a QR front. It means that I can just carry a u-lock and when I lock up, just pull off the front wheel and lock it up with my rear.