It's unlikely the case would still be open if it was several years ago, and you would have been a respondent in those proceedings, so if they were still under way, I expect you would have knowledge of same.
If I were in your position, I would contact Legal Aid to organise a family dispute resolution conference, which is mandatory before an initiating application for parenting orders can be filed. Legal Aid will do the legwork for you - they will attempt to contact the mother on your behalf, and will generally use all avenues available to them as a government agency. If they're unable to get in contact with her, you will be issued a section 60I certificate, enabling you to file an initiating application with the court.
You are expected to use your best efforts to have the other party served with the application, but the court has provisions for when a party cannot be located, such as substituted service or you can apply for dispensation of service.
Contact Legal Aid first. They offer free consultations for family law matters. It would be worthwhile getting legal advice and starting the process for family dispute resolution.