By default Windows doesn't recognise file systems formatted using Linux ext, however, Images containing Linux ext file systems can be browsed by using a free Windows driver.
Download Ext2Fsd from here: https://sourceforge.net/projects/ext2fsd/
Once downloaded, run the installer accepting any defaults. 
De-select launching the volume manage as this isn't required.
Linux ext partitions in Macrium Reflect image files can now be mounted and explored.
See also: Linux ext file systems can show a larger used and total space in Macrium Reflect