The 500D supports SDHC cards up to max. 32GB

The camera supports SD memory cards and SDHC memory cards (not SDXC). See operating instructions on page 2.
Operating instructions: https://de.canon.ch/support...
In the table of contents:
See "Card" pages .2, 13, 31
Reminder function .31, 130
Format 40
Problem 32, 209
SD speed class 121
SDHC 2

There is a write-protect switch on the left-hand side of the SD memory card. Make sure that the write-protect switch is pushed up (unlock position). You will not be able to change or delete the content on the memory card if it is locked
https://www.digitec.ch/de...

if there is no "format" function on the camera, you will have to format it using a PC

if there is no "format" function on the camera, you will have to format it using a PC