i have iphonex, I forgot the passcode. had to restore and it wiped off my data. I cant log in to icloud because i cant remeber the old passcode.How can i recover the old passcode

See If you forgot the passcode for your iPhone, or your iPhone is disabled https://support.apple.com/en-us/HT204306

The instructions are essentially the same for an iPad and iPod touches. “If you enter the wrong passcode too many times, you’ll see a message that your device is disabled. If you can’t remember your passcode, you'll need to erase your iPhone, which deletes your data and settings, including the passcode.”

If you backed up your iPhone, you can restore your data and settings after restoring your iPhone. If you never backed up your iPhone before you forgot your passcode, you won't be able to save the data on your iPhone. Follow the steps below to remove your passcode.”

Next, remove your passcode (see the document for the steps). Then, restore you phone of your computer (see the document for the steps).

“If you can't update or restore your iPhone using recovery mode, or you can't use recovery mode because of broken or stuck buttons, contact Apple Support. Then follow the steps to set up service for your iPhone.”

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Also, If you have iOS 11 or later and your account is protected with two-factor authentication, use get help with a forgotten passcode or disabled device.

There isn't a way to recover a forgotten passcode. If you see an option to reset encrypted data, several people have posted they did that and lost little to no data.