Different concentrations of the same organism, so they swap - but NOT 1:1.
The working conversion: roughly 1 tsp fresh yeast ≈ ¾ tsp active dry ≈ ½ tsp instant. Instant is the most concentrated (finest granules, most viable cells per gram) and mixes straight into the flour. Active dry is coarser, traditionally woken up in warm liquid first. Fresh is the bulkiest, loveliest and most perishable.
So for your situation - recipe says instant, you have active dry - use about 1.5x the instant quantity and give it a few minutes in the recipe's warm liquid to wake before it joins the flour. Same dough checks apply afterwards: the doubling and the jiggle don't care which yeast got you there.
Write the ratio inside your recipe book cover. This conversion question returns forever 🙂
