Front conversion has two options:
- a through axle to convert 15mm to 9mm, part # HRCXXX00N4369S (~17 Euro) - you can get non genuine ebay knock-offs too
- QR end caps, part # HWGXXX00S3801S (~30 Euro)
Or you could just buy a whole new QR 350 front hub with the end caps you need for about ~40 Euro, swap out the end caps and sell the new hub with your existing 15mm end caps
Rear is an end-cap swap, but you'll need a Shimano or SRAM specific set:
- For Shimano freehub end-caps: part # HWGXXX0001528S (~23 Euro)
- For SRAM freehub end caps: # HWGXXX00S3115S (~25 Euro)
All are available from the Germans - bike-components.de (their prices quoted above) and/or r2-bike.de - they'll be your best bet if you want/need to buy new.