It would be more cost-effective to buy a new one off the shelf, but add your existing hard drive to the case.
And SSD as first drive (C) will really speed things up, especially boot times. An SSD is basically a hard drive that doesn't spin.
With Win10 soon to be unsupported, you will no doubt get Win 11 which can be a big change for people with older versions. It says it only needs 4Gb of RAM, but 8Gb or more would really help it if you run multiple programs at a time.
2 companies we use in this family are:
https://www.cyberpowersystem.co.uk/
https://www.pcspecialist.co.uk
But Currys sometimes has good offers
https://www.currys.co.uk/computing/desktop-pcs