Jenkins said "I just think we have got to put the work in over the next week to make sure we are ready for Fiji. It would be so disappointing if we lost against them having come this far in the tournament.
"We know Fiji is going to be a tough game so we can't relax after the win tonight."
The prop did allow himself a moment to reflect on the second half try he scored as Wales romped to victory against Namibia.
He said: "I think I ran about 25 yards but by the end of the night I am sure it will be more like 60 yards. I don't get on the try scoring sheet often so I am pleased that I got across the line for this score."
His fellow try scorer, centre Scott Williams, crossed for three tries as Wales cut loose against their pool opponents.
Williams said: "I thoroughly enjoyed scoring my tries but all the boys played well in this game.
"We went out and did what we were supposed to do which meant we ended up getting a good result. Now we need to get back on the field and make sure we win next week.
"We knew Namibia would be in the game for the first half but it was important we didn't rush things. We knew we had to be clinical,"