Hi Sharda,
Although I'm not 100% sure exactly what the difference between your tablet and the M10 HD version, I'm hoping these guides will be close enough to let you fix your tablet.
First off, on the M10 HD (and hopefully yours as well), the charging port is mounted on a daughter card that can be fairly easily replaced. Here's a guide showing you step by step how to do that job.
[link|https://www.nadiemellamagallina.com/en/manuales/tablets-2/lenovo-78/lenovo-tab-m10-hd-1276/placa-auxiliar-11368|Manuales / Lenovo Tab M10 HD / Auxiliary board]
With regard to your volume button, it depends what part of it is broken. There's the physical button you push, then there's a tiny circuit board with the electrical switch mounted on it. Both of those are fairly easy to replace, but have different guides for each procedure.
[link|https://www.nadiemellamagallina.com/en/manuales/tablets-2/lenovo-78/lenovo-tab-m10-hd-1276/pulsadores-laterales-11372|Manuales / Lenovo Tab M10 HD / Side push buttons]
[link|https://www.nadiemellamagallina.com/en/manuales/tablets-2/lenovo-78/lenovo-tab-m10-hd-1276/teclas-laterales-11377|Manuales / Lenovo Tab M10 HD / Side keys]
The first one is for the electrical part and the second guide is for the buttons themselves.
Hopefully that will give you the information you need. With regard to parts, your best bet is to search on sites like Amazon, eBay and AliExpress for your model number together with the name of the part, although if you're okay with shipments from Spain you can order two of those parts through their website.