A 13.8 volt radio battery from 18650 cells
The short answer: Don't even try

Using Li-Ion batteries in a pack requires a BMS at least, using parallel cells even more so.
Connecting cells in parallel wil result in very high currents from one cell to another, resulting in (more) damage to both cells, even when the voltage differs only a few mV.

Constructing a working pack of different, possibly damaged, cells is very dangerous, even an almost depleted lithium cell can generate enough heat to get in thermal runaway. This can in turn heat the other cells enough for them to explode.

If you want to do something useful with these cells I suggest limiting yourself to a single cell at a time, and even then be careful.