If you need to get this information after the jobs have finished executing you will need to find the 'RunInstances' events in the CloudTrail logs.

Go to the CloudTrail console -> Event History, then search Event name 'RunInstances', then click on 'Filter by date and time', in the filter dropdown click on 'Absolute range' then adjust to start and end date times to the time your job started.

Your should find the entries in there and the instance type will be specified in the JSON.