how do i change the amount of babies i have in the sims

@MiraMim2019, I am assuming you mean to change the amount of babies you have with each pregnancy (singletons, twins, triplets).  While there might have been a cheat at one time, but since there were a bunch of cheats (including pregnancy cheats) that were accidentally allowed, they have since been removed. But you can still do certain things within the game to increase the chance of having multiples in a pregnancy:

1) the Sims who are the Mom and Dad of the family can use their Aspiration Reward Points to purchase a Fertility Trait that will increase the chance of conceiving, and also increase the chance of twins and triplets! On your screen on the bottom right there is the Aspiration button (hexagon shape).  Click on that and then click o the Rewards Store button (looks like a gift).  From there you can scroll down to "Fertility" -- it cost 3,000 Reward Points.

2) You can also give your lot a Fertile aspect by going into Build/Buy Mode and click on the Lot Info Panel (looks like a house with the letter "I" on it) in the upper left corner, and click on one of the hexagons and then scroll to find the lot trait called "On Ley Line" (looks like twin babies with a green plus sign).  {Also, if you have the Vampires GP, there is also "On a Dark Ley Line" if you want to regular Sims to have a chance to have Vampire babies, but that isn't what you want right now. 😉)  }

There might be more ways that I'm not aware of, but these are the 2 ways that are most used to get twins and triplets in the game.🙂

Beyond that, if you want even higher amounts of multiples in one birth, there are probably Mods that exist, but I don't play with Mods.  They require a lot of upkeep! 🤒 Every time EA update the game with a patch, there is a chance that your Mods and Custom Content (CC) can be come broken/outdated.😢  Broken/outdated CC/Mods can mess up your game. 😞 The Mod creators have to update their Mods to keep up with EA, and then the Mod users need to keep up with the updates.  And the way Mods can mess up your game can be unpredictable, which makes it more difficult to track down which Mod/CC is causing the problem.  You wouldn't think having CC eyelashes could interfere with something like walking you dog, but these kinds of things happen with Mods/CC! 🤨  I'm too lazy for Mods 😳 , but if you are very diligent and organized, Mods/CC can be a lot of fun. Just know what you are getting yourself into! 😉

Happy Simming! 🥳