how to get the administrator permission

[Mahesh S]

Add your username into 'jira-administrators' group in JIRA Administration -> User Management -> Groups -> jira-administrators -> Edit members.

But, this should be added by an existing JIRA administrators who has access to this.

[Nic Brough -Adaptavist-]

Ask an existing administrator to add you to the administration group.

Note that you don't get system-admin on Cloud, it's restricted to Atlassian Cloud Support only.