I always throw away all the stuffs that I don’t need.
I always throw away all the stuff that I don’t need.
Then I put each stuff where it belongs.
Then I put each thing where it belongs.
Stuff is an uncountable noun, so it does not normally have a plural form: ‘some stuff’, ‘all this stuff’, not ‘stuffs’.
Do not use each or a/an directly before stuff. Use thing or item when referring to an individual object: ‘each thing’, ‘an item’.