I see around 38 GB occupied by photos under storage on my Macbook but when I open Photos library or iPhoto Library there is no photo in that. where can I find the photos that is taking this space

Is it possible it is still in the recycle bin?

If not, then get the free app Disk Inventory X, and let it scan your drive. It should be able to tell you where the space is being used.

http://www.derlien.com/index.html

Did this problem arise after a system update or upgrade? Do you have a backup of the library that was made just prior to this first occurring? If you do restore the library from the backup and see if it has your photos in it.

Launch Photos with the Option key held down and see if there are more than one library shown in the Open Library window.

Have you rebooted? You should try booting into Safe Mode (How to use safe mode on your Mac - Apple Support) by booting with the Shift key held down and check there to see if the problem persists.  Reboot normally and test again.

NOTE: Safe Mode boot can take up to 10 minutes as it's doing the following; 

• Verifies your startup disk and attempts to repair directory issues, if needed

• Loads only required kernel extensions (prevents 3rd party extensions from loading)

• Prevents Startup Items and Login Items from opening automatically

• Disables user-installed fonts 

• Deletes font caches, kernel cache, and other system cache files

Where are you seeing this value for photos, i.e. the size of the Pictures folder? If you've deleted the library after copying to the EHD then it's gone?

If you're seeing that value in the About This Mac/Storage window it's including all image files on the hard drive, in apps, in the system, etc.

Do you rely on that. Did the free space change in the Info pane for your hard drive?

That is where you get the most accurate info.

Try reindexing the drive for Spotlight: How to rebuild the Spotlight index on your Mac - Apple Support