Is it possible to get my Snapchat login details on my iCloud?

If they were saved to your iCloud Keychain you can go to Settings ➜ Passwords on an iPhone or iPad or use the Keychain Access app on Mac and see if Snapchat is listed there.

If its not there, then there is no where to recover the login details from.

You would need to go the Snapchat website and reset you password there.

https://help.snapchat.com/hc/en-us/articles/7012348977684-I-forgot-my-password-How-do-I-reset-it

Your question is not very clear.

Do you mean you want to save the Snapchat login details in iCloud Keychain?

Do you mean you are trying to recover said login details on iCloud website?

What exactly is the issue? Please explain in as much detail as possible.