Explorer's Cache — ruling 1

To move a counter from one permanent to another, the counter is removed from the first permanent and put on the second. Any abilities that care about a counter being removed from or put onto a permanent will apply.

Explorer's Cache — ruling 2

If Explorer's Cache isn't on the battlefield as its activated ability resolves, you can't remove a +1/+1 counter from it, so you won't put a +1/+1 counter on the target creature.

Explorer's Cache : règles, fonctionnement et interactions (MTG)

Explorer's Cache is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

This artifact enters with two +1/+1 counters on it. Whenever a creature you control with a +1/+1 counter on it dies, put a +1/+1 counter on this artifact. : Move a +1/+1 counter from this artifact onto target creature. Activate only as a sorcery.

How it works : Explorer's Cache

Original English text — Wizards of the Coast / Scryfall

#1November 10, 2023· Wizards of the Coast
To move a counter from one permanent to another, the counter is removed from the first permanent and put on the second. Any abilities that care about a counter being removed from or put onto a permanent will apply.
No other card is named in this ruling.
#2November 10, 2023· Wizards of the Coast
If Explorer's Cache isn't on the battlefield as its activated ability resolves, you can't remove a +1/+1 counter from it, so you won't put a +1/+1 counter on the target creature.
No other card is named in this ruling.