Always download and install video drivers from the card manufacturer, in your case NVIDIA.
Never install video drivers supplied by Microsoft, they will be out of date.
Rule #1 about video drivers: if they work leave them alone, don't update, don't touch them.
There may be newer driver versions available but they may not work with your old Dell OptiPlex motherboard chipset.
If they don't work then your screen will look like colorful wrapping paper. You will then have to figure out how to boot in Safe Mode, figure out how to uninstall the non-working drivers, download and run a driver deep cleaner, and re-install the old working NVIDIA drivers if you have them.