I would suggest having a look at https://confluence.atlassian.com/adminjiracloud/importing-data-from-json-776636779.html to import the project into JIRA.
Once in JIRA, it will be possible to convert the project into a Service Desk.
It might be useful to also open a Service Desk support ticket at https://support.atlassian.com to get some more personalised assistance with the process.
I can't importt from the JSON file. I guess that the JSON file export must contain the correct JIRA Project fields and not the Freshdesk fields.
I have also opened a ticket with :
See import error:
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