V5.0.0. Waauw, that is ancient. Looking back on the KiCad website, it was released on: 2018-07-22
I wonder why you never updated to newer KiCad V5 versions. KiCad V5 goes all the way up to KiCad V5.1.12, released over three years later on 2021-11-10.
First, a small recap of the KiCad version numbers. Currently the KiCad project is on a yearly release schedule for releasing a major KiCad version (The first digit) each year. This mayor release has all the new features which were programmed in the year before it. (Developed in the KiCad-nightly, which as a Vx.99 version number). Because of these big changes, it is also likely to introduce a lot of new bugs.
The second digit is for introducing new features in the same mayor KiCad version. After KiCad moved to releasing a mayor version yearly, this second digit is not expected to be used again and probably stays at 0. The third digit are bug fix updates. These are currently released about once a month, and it is recommended to always update when these get released. Currently there are usually over 70 bug fixes each month. Sometimes unforeseen things happen with these bug fix releases, and it gets pulled back. If you have a company that relies on KiCad, then it’s probably best to wait one or two weeks before updating to the latest bug fix release.
As I wrote before. KiCad V5.0.0 is quite old, and a lot has happened since. In KiCad V6 all the icons have been re-designed, and this makes KiCad look quite a bit different, and this will take some time to get used to.
The most important thing however, is that starting from KiCad V6 the schematic has a completely new file format. In this new file format (based on S-expressions) all schematic symbols are embedded in the schematic file itself, and this makes your KiCad projects a lot more robust. KiCad V5 did make [project]-cache.lib and [project]-rescue.lib files, and these are essential parts of the KiCad V5 projects. People often deleted the [project]-cache.lib file, and this seemed to have no ill effects, but that was only true as long as the original V5 KiCad libraries were still available. If both the [project]-cache.lib and the original libraries are missing, then a KiCad V5 project is severely damaged and it takes some significant manual intervention to fix that.
If your KiCad V5 projects are complete (so inclusive those files) then migrating your projects to KiCad V7 should be easy. The process is basically just 1). Open the project in KiCad V7. 2). Go through the rescue / symbol remapping. 3). Save the schematic. 4. Open the PCB in KiCad V7 and save it. The PCB does not need any special remapping.
Another noteworthy change is that the libraries have been updated, extended and improved. All (I think) SMT pads now have rounded corners, both on the pads themselves and in the solder stencil. This is an IPC recommendation that improves solder paste release and therefore a more consistent amount of paste on the pads. When you update a project, the old footprints are maintained. You can upgrade the footprints to newer versions, but this is a user decision.