Ideally, you would know how the weights treat you from a previous run through triples and singles.

But absent that, the general rule is to keep overall volume consistent: if you're doing three sets of five, move to five sets of 3. You might find 3x3 works as well.

If you're doing a single set of five for intensity, you can go 1x5, then 2x3, then 5x1. Preserving overall reps, but increasing intensity.