Request for help in /spawn command

Hi! I'm working on a mod that adds a /spawn command. It would be capable of doing the same thing as the /summon command, but with an additional number at the end to specify the quantity to summon. I've created the new command, but I'm unsure how to specify the entity type I want to summon and incorporate it into the procedure. I managed to include the position where the entity should be summoned (Block position parameter), but I'm struggling with determining the entity type. If anyone has any ideas, please let me know!