Correct nozzle replacement
This is a so-called MK10 nozzle, it is larger than the normal nozzles you find (as you found out).

There are quite a few questions on this nozzle, with e.g. this answer or this answer.

This nozzle uses M7 (metric threads of 7&nbsp;mm) to have more room to fit the PTFE tube (white tube) in the nozzle itself. This tube forms the barrier between the heating source and the filament feed so that it does not melt too soon. You can find these nozzles on those typical auction websites by searching for "MK10 and M7".

When you have ordered the correct nozzle you could reuse the existing PTFE liner if it has not degraded or damaged, or buy replacement PTFE tube of 4&nbsp;mm outer diameter and 1.9 or 2&nbsp;mm inner diameter and cut a similar sized replacement liner.