The Dell support web site has articles which usually include pictures for what you want to do. Depends on your model how easy it is. Also depend on whether your hard drive is a disk or NVME memory. A disk on the Dells is usually a matter of unscrewing a hatch on the side and replacing the disk in the enclosure caddy. If it's NVME, that might be on the motherboard and you're out of luck swapping it. RAM memory might be under the keyboard, in which case you gotta unscrew like 20 things and get under there with a precision sized screwdriver. Search for "replace RAM (or hard drive) model ____" on their support site.
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Jeebus man, that's confusing.
To the OP...
Sounds like you want to increase your hard drive capacity. Memory (RAM) is a different thing.
You'll have to copy your Operating System and your files, apps to your new hard drive.It's not a simple, turn-key process unless you have some hardware and software experience.
Without some skill in those areas, it will be best to take it to a qualified tech.
Another way to increase storage is to use an external hard drive or thumb drives.
Talk to your tech about it, these may or may not fit your application.