There are a lot of mods I want to port, but I don't know how to go about it and do it properly to avoid crashes, etc. Could you put all of the steps and relevant information here so I can use it as a future reference? I am trying to port a major mod with scripts, 3d models, new items, new spells and whatnot.
While the comments sum up how this question isn't particularly valuable for this site I will add an answer that I think can be valuable for those searching the same thing.
Many (I would go as far to say a majority) of the mods available on the Nexus for Skyrim SE are ports of existing LE mods. In fact, if you head over and look at both Nexus sites you'll find many of the "New Files" and "Hot Files" are on both, because modders tend to create them for both games simultaneously. As such, you have a plethora of existing sample cases to learn from.
Download mods from both sites that have parts of what you intend to do and examine the differences. If you want to port a mod that adds new models, find an already ported mod that adds new models. If it's scripts then do the same with that. Many mods will only need opening with the SE Creation Kit, then saving anew, to complete the port.
A key outlier here is mods that use SKSE. SKSE had to be entirely rewritten for SE and was renamed SKSE64 (because SE is 64 bit, compared to 32 bit LE). As such, while the developers of SKSE intended to create the plugin with an identical API to LE it's vital that all usage of SKSE within the mod are completely checked in-game running SKSE64 to ensure they work. Otherwise the scripts will need to be modified to match the new API.
Another point is to look out for dependencies. It's great if you port a mod to LE but if it has a dependency that hasn't been ported you'll have trouble running it (or parts of it) at all. Make sure any dependencies have been ported (by yourself or someone else) and that all references within the mod point to the ported dependency.
I would say to just dive in. Start with an LE mod loaded into the SE CK and save it - see what happens when you run the game. Troubleshoot any errors and if you can't find an answer, by all means come back and ask another question here (with a more specific problem in mind!).