Hi Is it possible to connect the internal hard drive to STM32 ? How?

[Jeroen3]

It is theoretically possible to connect a SATA hard disk using an USB to SATA bridge IC.

The STM32 must work in USB host mode, and support the device class of the hard disk.

If it is any practical, I'm not sure. It will be pretty slow, and you can't use GPT or NTFS unless you find firmware for that.

[Tesla DeLorean]

IDE ones would be easier.

On the platform people typically use eMMC or microSD cards. You could add 400GB​ to a project that way.

[waclawek.jan]

Internal to what? Try to describe your idea in one-two sentences.

JW