Hi there Beatrice! My name is***** am a computer professional with over 15 years of experience with both Mac and Windows computers, phones, tablets, and printers. It would be my pleasure to assist you with this. Let's start with the easiest things first to try to narrow down the cause.
Press and hold the Power button for a full 40 seconds until your device restarts. Plus the kindle in to the wall charger and let me know if you see a green light indicating that it is charging. If this has no effect, please connect the Kindle to your computer using the usb cable that came with your Kindle and repeat this process.
At this point, if it is still not turning on, please allow it to charge for about 15 minutes and try once more to turn it on.
If still no luck, please let me know the exact model of you Kindle fire. If you aren't sure please login to your Your Amazon account and go to Manage Content and Devices, click on device tab and tell me what you see there.