Briefly, this is usually done with a device generically called a "deserializer". The core component of a deserializer is a circuit called a "shift register" (or firmware or software that performs the same function).
You can think of a shift register as being a little like an old-timey firefighting bucket brigade. Now imagine that instead of buckets of water being delivered to the far end and emptied one at a time, the buckets are kept in the brigade as the "slots" are filled, then emptied all at once.
The first bucket - bit - that's entered into the s.r. gets passed down the line and ends up at the far end. The next bit ends up in the position next to the far end. Etc. When 'n' bits (for an n-bit parallel bus) have been clocked in, the register contents are copied out, all at once, to the parallel bus. (As if the volunteers in the bucket brigade all dumped their buckets out at the same time, in the same direction.)
If you want to know more about this, learn about "D" flip-flops and then shift registers. I suggest Don Lancaster's classic TTL Cookbook, chapters 5 and 7. Don has now made this available as a free download: https://www.tinaja.com/ebooks/TTLCB1.pdf