SSD in place of HDD - Hello. I would like to replace my HDD with SSD.

Hello and I am asking for advice.
I will present the matter from the beginning.
My equipment in the attached photo.
I want to put an SSD in its place instead of the standard HDD. It will work as a system one. Since I have a lot of cool stuff on the HDD, I want to keep it and have it for use not in a portable USB pocket but in a laptop. I was thinking of an adapter instead of a DVD. Does anyone have such an adapter and it works? I know that this is not the purchasing department, but if someone gave me the link, I would be grateful. Since I live in the UK, I cannot buy in Poland. I cordially greet everyone. Certainly there is someone who will advise you without closing the topic, admonition, entry in the file, etc. I hope that I made a gross spelling mistake. I use an English keyboard and language, so a trick can happen.

Hello. I use such a pocket in Lenovo Z710.
SSD disk mounted in place of standard HDD, HDD in the pocket due to the fact that the SATA port for the disk has more bandwidth (SATA 2 vs SATA 3)
Boot works from any disk, but it is worth the whole system to be on the SSD disk.

The only thing you need to know is the height of the drive so that the pocket fits in this place.
The front of the drive can be put into a pocket so as not to spoil the aesthetics of the laptop.

I know there are probably 11.5mm standard drives and for Macs. So everyone should fit? I put a disk in it and put it in my laptop and recognize it as hard?

At least enter the name of the laptop. We do not know the size of your drive, and how should we know it? And the dimensions are different from 9mm, and in strange designs where there are slot drives even less.

The laptop is the Acer Aspire 5750G. I'm sorry, but it doesn't matter. Pockets should fit all "fat" laptops.

Probably 12.5 mm - but pull out the drive and whatever you measure the thickness of the drive, you will be 100% sure. Because there can be 9.5mm even a drive.

A pocket like a pocket - as long as the thickness is correct and it should work. ebay, aliexpress it all depends on whether you give more or less, but it will go longer.