my macbook air starts with blank screen and I manage to go to utility page but when try to reinstall the os it can not find the internal hard disk when reinstalling

You are missing some very important details:

• Exact model of the Mac
• Version of macOS last used
• Version of macOS that is going to be installed
• Have there been any hardware modifications or upgrades?
• Why are you trying to reinstall macOS? That reason may be why you are having problems here now.

You can get the exact model by entering the system serial number on the check coverage page here (please do not post your serial number on the forums since it is considered personal information):

Check Your Service and Support Coverage - Apple Support

While in Recovery Mode, launch Disk Utility. If there is a "View" option just above the left pane of Disk Utility, then click it & select "Show All Devices" so that it reveals the physical drive and other hidden items. Post a picture of it.