Sizing Through-hole Vias for Power Traces
The plating thickness of a via is typically circa 20µm, or roughly equivalent to 0.5oz copper.
Given the via is a cylinder, the width of a via can essentially be considered as the circumference of the drill diameter, so: \$\pi\times d\$.
We can calculate then that, a 0.4mm via drill will be roughly equivalent to a 1.25mm PCB trace on 0.5oz copper, or for 1oz copper equivalent, half that (0.63mm).
For your 2mm wide trace, assuming 1oz copper, four 0.4mm vias would have a roughly equivalent current handling capacity. Alternatively you could use a single via with 1.27mm hole diameter.