Why when i tried to update my apps its showing that i need to enter the password of the previous apple id
Did you change your Apple ID? If yes, see What to do after you change your Apple ID or password https://support.apple.com/en-us/HT204071
If you created a new Apple ID, those purchases are tied to the other ID, and can't be transferred. One option is to delete the apps/purchases made by the other ID and download them using the new ID if desired. If necessary, check your purchases history to see which apps/purchases weren’t made by the current ID.
Purchase History Review. https://support.apple.com/en-us/HT204088
Difficulties on updating apps
