Help creat pokemon

[Kunal]

I am trying to creat ultra necrozma in my sword and shild save file but there are many errors (I am new to it so pls help in detail) so can someone tell me how I can do it

[Shady Guy Jose]

There are several problems with that. First, Ultra Necrozma isn't even in the Sword/Shield game code, so editing your save would never work for that.

Second, even in Ultra Sun/Moon, Ultra Necrozma is a battle-only form. It will never be legal in PKHeX. You would need to create a Necrozma and a Solgaleo/Lunala, fuse them with the appropriate items in-game, give the resulting Pokémon an Ultranecrozium Z, then activate it in battle. But even creating a Necrozma and one of the other two is hard, the best way is to catch them naturally and then edit the stats, or download .pk7 files from this site.