Sadly it’s not as simple as just soldering on a Qwiic connector.
The device you want to convert to qwiic is just a bunch of regular old switches, it doesn’t have any intelligence or a way to communicate over the I2C bus that qwiic is built on. At a minimum you’re going to need some sort of micro controller to read your switches and then convert that into data packets that are suitable for transmission over the qwiic bus.
This is going to mean writing code that does the translation and communicates via I2C, and that’s going to take some work but is possible. Arduino has a small tutorial that scratches the surface of what you would need to write codewise, you might check that out.
If you want something simple, five Qwiic Button Breakouts that all have unique I2C address programmed would do the trick but it’s a bit bulky and cumbersome.