In short you do not. There is no magic tool to reliably convert between packaging formats such as .deb/.rpm and there never will be.
You can of course do it if you want to learn packaging for Solus which is not something that most users are going to want to do and is a manual process https://getsol.us/articles/packaging/ here is an example of how we write a build recipe when repackaging is required (usually due to the software being closed source and only provided via .deb/.rpm) https://dev.getsol.us/source/vivaldi-stable/browse/master/package.yml there is no easy universal way to do that for every bit of software you just have to know what you're trying to achieve and figure it out for that package.
You can however also try avoid this and extract the contents of the files to somewhere in your home directory and run the executable directly, hoping that it works. While this will often work its not great and if you rely on .deb/rpm's I would just use a distro that uses them.
EDIT:
There is of course flatpak/snap/appimages if they are available that would also avoid needing to do any of this.
