Lost some space on External hard Drive.

I have a 1 TB Segate extrernal hard drive. I have portioned this into 4 (32 GB) fat 32 file system and 1 NTFS file system partitions. However I do not see the 2 (32 gb) partitions on the hard drive anymore. Even on disk management it does not show these partitions, where did it go ?
The disk total capacity shows 1tb but used and free space available is 930 GB. How can I get hold of the lost space? I tried to use the extend command from Disk Management and giving it the 70 GB space to expand but no use.
Can somebody help me recover the lost space please?
Thanks in advance for all the help.

Regards,
Utkarsh G