You’ll need to ask your DM.
5E has no general provisions for collecting parts of dead creatures and assembling them into new equipment; the assumption is that basic equipment is purchased or crafted - both with gp - and advanced equipment (magic items, etc.) is found during your adventures.
If you want to craft your own items above and beyond regular gear, you’ll need to ask your DM. They may be able (and if they’re like me, willing or even thankful for the inspiration) to create a quest for you to do so.