Topic category: User side tutorials
First, get blockbench. It's a very useful modelling tool.
Blockbench also has many plugins. One of which is the "Bedrock entity generator". I know it says bedrock, but the models work for java. Trust me, I use them in my mods
You can find this on github, along with all the other plugins.
To install it, you go to the "Filter" tab after downloading the plugin, click on the puzzle piece saying "Plugin" and click on the source code icon by the word "Plugins"
Highlighting it will then say "Load Plugin from File"
Then you can actually locate and load the plugin.
After that is done, it's time to make a modded entity!
Then, click "Create new modded entity" once you have finished the installation.
(It should be the third option on the menu)
Or you can click "File" and "New" and choose it from drop down menu
Name it as you please
Be sure once you're done to rename it as loading a model changes the geometry name for some reason
Anyway, click on "Filter", and you will see "Bedrock Entity Generator"
Clicking on this gives you a dropdown menu of TONS of mob models. Once you select the one you want, be sure to check "Create entity model"
Now you have your base model!