just got a new chain and back sprocket last year so I should be fine. the front one is still fairly new.
I hate to tell you , but it just dont work like that.
I have some sad news for you.
You should never mix old sprockets and chains with new or second hand ones.
They marry for life, and do not take kindly to another partnership.
A new sprocket will quickly wear/stretch or break an old chain.
A new chain on an old sprocket can be completly stuffed in a few miles.
An old chain on a new sprocket, the sprocket will have trouble meshing with the chain and will be stuffed after a few miles.
Rule of thumb, always replace the whole set, chain, front and back sprockets.
Ignore the rule and be prepared to either punch a hole in a case due to a broken chain, or have the chain wrap around a part of your anatomy at speed, very painful sometimes fatal.