My 1tb external drive only see 36gb

Go into Control Panel/Administrative Tools/Computer Management/Disk Management. With the external HDD connected, you should be able to see what partitions/free space is on the drive. I suggest you remove all existing partitions and then format the drive in one big NTSF partition (just easier to manage). You can, however, make as many partitions as you desire, up to you.

Good luck!