If you work at an organization certified several years ago you already have experience as an internal auditor at your own organization. What I can recommend is following two parallel ways:
Contact your professional network and offer your services to perform internal audits at other organizations: That will give you valuable experience in contacting other management systems, and different interpretations and uses of the management system standards; That will train your communication skills with strangers.
Enroll in a certified and recognized Lead Auditor Course, like this one from Advisera - ISO 9001:2015 Lead Auditor Course - https://training.advisera.com/se/iso-14001-internal-auditor-course/o-9001-lead-auditor-course/ - and offer your services to certification bodies (your experience as an internal auditor at several organizations will be highly valued)
2. I would like to become a trainer on QMS and EMS what will be the steps?
I assume that you don’t wan t to be a full-time trainer. So, in that case, you should list and contact training or consulting organizations in your country that could be in need of an experienced practitioner. Many times, trainers have no hands-on experience, you can and should use your work experience as a competitive advantage. If you feel you need to certify your knowledge about management systems standards you can enroll in this course ISO 9001:2015 Foundations Course - https://training.advisera.com/course/iso-9001-foundations-course/