When i connect my hard drive to my laptop it does not show how much data on my hard drive and it has asked me to format my hard drive

Is it a "brand-new" external storage device? If so, then it must be "initialized" before being used for the first time.

If you have been using it, then the "Table-Of-Contents" on the disk-drive has become corrupted.
Since Windows does not recognize the data as being a valid T-O-C, Windows is asking your permission to write a new, valid, empty, T-O-C onto the disk-drive.

Perhaps, all the other blocks of data existing on the disk-drive are still valid.
Look online for a "file recovery" or "file scavenger" program,
which reads through the disk-drive, block-by-block, trying to "stitch" the blocks together,
to reconstruct your files.