what you have, and the PSU you are after, is called an ATX power supply.
they are all the same, standardised dimension to fit in your case.
it will have a 24pin power cable that connects to your motherboard and has been standard for more than a decade, so unless your future motherboard changes how it gets power, the new PSU will do you for many years.
all those cables can be daunting, but take pictures of the current setup to aid you.
you simply take one cable at a time, the good news is, they are designed to only connect one way into the appropriate socket. as long as you don't use heavy force, it is impossible to get it wrong.
the biggest task will be cable management - getting all the cables to snake around the insides to make it look tidy and not block airflow too much. some cable ties may help with this.
there is a new standard trying to get traction right now, the new 12VO (volt only) ATX models. it has a 10pin motherboard power connector rather than the current 24pin.
current PSU's have 3.3, 5 and 12 volt rails.
ATX12VO, as name suggests, only has 12v, since few components in a PC these days use the older 3 and 5v rails off the PSU. so they are trying to reduce the size of the mobo power connector (for some reason).
however SATA devices still use 5v, so they have the power connectors for these appear on the mobo rather than needing a cable back to the PSU.
but with all PC standards of the past, it takes a generational shift before they even start appearing, let only being dominant.
ATX12VO standard was released in 2019.
good article here;
https://www.overclock3d.net/reviews/power_supply/atx12vo_tested_-_the_future_of_power_supplies/1