Based on my experience I suggest migrate only close/resolve tickets and let the support team close the already open tickets in old tool so that they won't miss SLAs
First check the data model for both these tools
Create a field mapping document and map the field values and types
Check if the filed type matches a choice field in Manage Engine can be a reference field in Servicenow and vice versa, document the approach how will transform the data
Check if Choice Field values and reference record exist
Example Assignment group, priority, category, sub category, resolution code, Configuration Items etc
If you don't have the matching value then you need to finalize the mapping with existing values and get sign of for the field mapping and field values mapping from the stakeholders
Also, set the expectations if there is any major gaps
You need verify the foundation data matches like Users associated with the ticket records and their department, Location etc exist in Servicenow otherwise it won't map on the ticket data
There may be tickets associated with terminated users who have left the company you need to check with stakeholders if those tickets need to be migrated
If my response helps to solve your issue. Kindly mark it as helpful & correct and accept the solution. It will be helpful for future readers!
