We inherited an EE site, and are working with the client to upgrade from v2.10.1 to the latest v5. We are working on the initial 2->3 upgrade and found some instructions here.
Step 4, unfortunately, has a broken download link:
Download the latest release of ExpressionEngine (either ExpressionEngine Core or the standard edition, whichever your site is currently running) and unzip the files to a folder on your computer.
I assume since these are dated instructions, when they say "latest release", they actually mean download v3.5.17.
Where else might we get the files needed?