It does have one M.2 slot, SATA only (no NVMe).  
I have vostro 3478 model, Having i5 8th gen processor and 8GB RAM. I want to know that does my laptop has additional slot for M.2 ssd . Which type of ssd does it support.   Please help.
Does my Vostro 3478 with Intel I5 8th Gen processor support m.2 nvme SSD