You will not lose any information when you import data from Jira to Yodiz. Import only copies data to Yodiz. Although, some Item Types will be changed after import. Details are:

• Sub-Task from Jira can be mapped to Task in Yodiz.
• Versions in Jira are called “Releases” in Yodiz.
• All the attachments, comments and associated workflow is migrated from Jira into Yodiz as it is.
• All standard custom fields from Jira, except Date-Time Picker & Select List (cascading) are imported into Yodiz.