Just to let you know . I’ve never had or worked with S-VHS-C tapes.
I think the best way with what you have is to get a video card with s-video input.
Then a sound card with RCA in .
I assume that the white audio port out is Mono.
Then you need some kind of “capture” software .
There are a lot of them & I don’t know the best one.
Even the freeware VLC player has some capability to do this but a paid software might give you more setting selection & better quality.
If the Audio track is seperate or you seperate it . You could use a program like Audacity to duplicate the mono Audio track for a two track sound . Then Mux .
That might sound better on modern equipment.