How do I cancel my individual Apple Music as my wife has a family plan we are paying for

Please read this link to learn how to view your subscriptions that renew automatically, change your subscription period, and turn off Automatic Renewal [essentially "canceling"]. --> See or cancel your subscriptions - https://support.apple.com/HT202039

According to the footnote in the "First, set up Family Sharing" section of:

Get an Apple Music family subscription - Apple Support

If someone in the family group already has an individual or student subscription to Apple Music, renewal of that subscription is automatically canceled when they join the family group.