I received the SD card but it is too big to fit in my GPS.

What you received is a microSD card in an adapter. The adapter makes a microSD card big enough to fit in units that require standard size SD cards. The adapter also helps to protect the microSD card during mailing.

Since your GPS takes microSD cards, simply slide the microSD card out of the adapter and you will find that it is the correct size for your GPS.

Below are photos that may help to explain what you received. One picture is of the microSD card in the adapter and the other is of the microSD card by itself.