How to insert a comma into a string

Can you help me in
Make a string, pass the rtc time, add comma then 3 bytes of our data using esp32
How to do this?

Please post an example program showing what you are trying to do and the data types being used

@Hareemahsan

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Please do NOT cross post / duplicate as it wastes peoples time and efforts to have more than one post for a single topic.

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Bob.

You’re using the ESP32, so use a String, not a string.