Q: had my ipod stolen and need to change my passcode

All necessary info here: If your iPhone, iPad, or iPod touch is lost or stolen - Apple Support

Hi caravan1

I am not sure what you are asking. Are you saying the iPod has been stolen and not been recovered?

If so see here: If your iPhone, iPad, or iPod touch is lost or stolen - Apple Support

If you are saying it was stole and has since been recovered but the passcode has been changed then you need to restore the device:

If you forgot the passcode for your iPhone, iPad, or iPod touch, or your device is disabled - Apple Support

Since you said "I didn't set up find my ipod when we first set it up"

all you can do is:

lost/stolen                                     

No app on the iOS device is required.                           

- If you previously turned on FIndMyiPod/iPhone/iPad on the iOS device in Settings>iCloud and wifi is on and connected or cellular data is on and connected for, on a computer browser go to iCloud: Find My iPhone, sign in and go to FIndMyiPhone. If the iPod has been restored it will never show up or continue to show off-line.

- You can also wipe/erase the iOS device and have the device play a sound via iCloud.

If your iPhone, iPad, or iPod touch is lost or stolen

iCloud: Erase your device         

iCloud: Use Lost Mode

- If not shown, then you will have to use the old fashioned way, like if you lost a wallet or purse.

- Change the passwords for all accounts used on the device and report to police and carrier if iPhone or cellular iPad

- There is no way to prevent someone from restoring the erase (it erases it) using it unless you had iOS 7 or later on the device. With iOS 7 or later, one has to enter the Apple ID and password to restore the device.

- Apple will do nothing without a court order                                               

Reporting a lost or stolen Apple product                                              

- iOS: How to find the serial number, IMEI, MEID, CDN, and ICCID number