I have an Acer Predator G3-710 2016 (desktop) pc.
I haven't found the motherboard SPECS, but in the meantime I attached 3 photos.
Could it be that photo #1 shows the SLOT where the NVMe card plugs? (red rectangle)

According to laurent_14 from the Acer forums these are the available expansion ports in this pc:

SATA 3.0: 4
- ONE for DVD drive
- One for HDD drive
- 3 HDD bays so 2 free
M.2 SSD: 1 (SATA 3.0)
PCIe X1 3.0: 2
PCIe X16 3.0: 1

Thank you in advance guys
those are PCI express slots.
abbreviated to PCI-e or PCI-x.
the sort of NVMe you want for those slots are these (but it'll also depend of the PCI slot specs and the NVMe card requirements)

Yes- As Mark says, those two slots are PCI Express slots.

The motherbard has an M.2 slot. As per the specs there though it is not NVMe, it uses SATA 3.

As to where that slot is, You can see it poking out from under the graphics card just above and to the right of the battery in your first image. An NVMe Card would slot in parallel to the motherboard- not perpendicular LIKE expansion cards.Thank you so much for your help guys!
That's the info I needed to move forward.

I wouldn't want to abuse your kindness, but would you mind helping me out with this other but very similar post?
It's basically kind of the same question but for an older pc.

Thanks in advance,

DPC