Renan has a great answer, but doesn't consider magic. You've said that crews can magic back to safety if need be, so we can take advantage of this to massively increase our range. I'm going to use some assumptions here, but you can alter these assumptions based on your world.
Your exploration fleet is 25 ships. This is based on the size of the fleets the British Navy had during the age of sail. I'm not a historian, so please alter this to fit how many large ships your nation can build for this expedition.
You can crew these ships with a barebones crew of 50 men. This is based on Magellan's crew. He started with more than 200 and finished with 18. I'm guessing 50 could crew a ship effectively.
These ships can sail the Pacific in 3 months. This is also based on Magellan's trip.
Your ship can carry enough supplies to support 150 sailors for 3 months, or 50 for 9 months. This is also extrapolated from Magellan's expedition.
The width of the Pacific ocean is 17000km
You will sustain all of your crew members off the supplies of a single ship. When that ship's supplies are depleted, these sailors magic home, and the remaining sailors eat from the next ship, and so on until there is only one ship left.
Using the numbers from above, if you start with 25 ships, you have 1250 sailors. This math is very much like the Rocket Equation, but I'll do the math by hand for simplicity.
If 50 men can survive 9 months, then 1250 men can only survive .36 months. There's no more use for that ship or the men, so they magic back and there's only 1200 men. These 1200 men can survive for .375 months and so on...
Now we sum the whole thing and get 34.34 months of sailing for the last ship. If Magellan's ship could go 17000km in 3 months, then this ship could conceivably have traveled 194593km in its 34.34 months. That's with a lot of guesswork, but you can use my method with whatever numbers you have to get numbers you think apply to you.
Edit: In the comments a number of limitations have been raised - I'm pulling them in to the answer because they're valid concerns.
This doesn't take into account the fact that supplies -- even fresh water -- have shelf lives. Spoilage and/or loss to mice, etc., will take a toll. As will ship repairs after any storms, etc.
Sailing is not only about supplies. You have to repair the ship sometimes. You need to remove barnacles from the hull periodically, for example, or else the ship will become slower. Sailors of old did so by careening their ships, which can only be done on shallow water. Bottom line: your food may last for years, but if you don't stop here and there every once in a while your ship will deteriorate as fast as if it had been abandoned.
Consider that both of these need to be addressed to make this strategy viable. It's my opinion that they can be solved with magic, since your world allows it. Otherwise, you'll have to find a non-magic solution to these problems, which may or may not be possible.