Where can I connect a hard drive to my laptop?

My laptop has room for an additional 2.5 "HDD, but somehow the connection is missing, right?

There's a cable missing, can you do this with Acer? Reorder. The HDD / SSD can then be connected to Sata. At least, I suspect.

So is that a SATA connector? Incidentally, it is an HP laptop

I only find the M.2 with 256 GB

Yes, but you need the exact model. HP. It says on the battery, I could have put it myself. ^^ Have a look on the HP page if there are any accessories.

Because you can't connect another hard drive… Only the M.2 - have googled

No, it's not for Sata. A Sata connection looks different.

Here is such a Sata cable but you need something that fits in length and you should look at HP with the exact model name and the right connector. So don't blindly buy this on Ebay.

https://www.ebay.de/...1977389453

The offer is only for understanding, with laptops sata plugs look different than on the PC.

The offer is only for understanding, with laptops sata plugs look different than on the PC.

That is clear to me, thanks for the hint anyway. FloppyDobby has already said his answer.