Acsess to my old iPhone and knowing the pin

If you had Find My turned on, you could log into the FindMy website using the Apple ID and Password of the device and erase it remotely. You will get a confirmation email sent to the email address of the Apple ID. The device will have to have an internet connection and will still be locked to your Apple ID.

Erase a device in Find Devices on iCloud.com - Apple Support

IF you had find my enabled, you can log into your icloud account at https://icloud.com/find and initiate an erase from there.