Spell Slots in D&D 5e: All You Need to Know!
See the multiclassing rules to determine your available spell slots. ... You regain all expended spell slots when you finish a Long Rest.
Warlock - bg3.wiki
Very closely related (about using Warlock slots to generate Sorcery Points, not using Sorcery Points to make Warlock slots): Can I use Pact Magic spell slots gained on a short rest to gain sorcery points?
D&D 5E - Short Rest Spellcasters (+)
Once per day when you finish a short rest, you can choose expended spell slots to recover. The spell slots can have a combined level that is equal to or less than half your wizard level (rounded up), and none of the slots can be 6th level or higher.