Per the trade value chart, the Cowboys could theoretically trade the #20 pick (850 pts) to Arizona for the 2nd overall pick in round 2 (pick 34 - 560 pts), and the top pick in round 3 (pick 65 - 265 pts), giving them 3 of the top 65 picks in the draft, plus their 6th round pick (186th pick - 17 pts). This would be a trade of 850 pts (#20 pick) to Arizona for their 2nd, 3rd, and 6th round picks (#34, #65, #186) which adds up to 842 points.
This would give the Cowboys picks in every round and multiple picks in rounds 5 and 7 - a Total of 10 picks.