need help on usb button box

hi all i sow some projects on button box up to 25 buttons, my project needs at least 35 buttons but it may need some more in future lets say up to 50, so my question is do i need to bay 2x Arduino Pro Micro boards an use 2x usb pors. or i can use like arduino mega? is it posible to connect more buttons to this arduino board?

so my question is do i need to bay 2x Arduino Pro Micro boards an use 2x usb pors.

No.

or i can use like arduino mega?

No.

is it posible to connect more buttons to this arduino board?

Yes, lots of ways, shift registers, SPI port expanders, I2C port expanders.