Welcome to the Community :)
I would check out all that Atlassian University has to offer, alongside certifications.
You could also create a free instance of Jira - or other products like Confluence and Jira Service Management - to try out some of the skills you'll learn in the courses!
welcome to the community
I would start with ACP-620 Managing Jira Cloud Projects
Later on i would focus on https://www.atlassian.com/university/certification/certifications/exam-acp-120
Generally speaking the Atlassian university is a great place to start incl. some free trainings
Hope that helps