Woocommerce order notification via sms

Hi, I need to send a sms notification to the client and shop owner mentioning the order number and order value once an order is placed through the website. I have used woocommerce plugin. I cant use a plugin to send sms since I have already purchased an sms gateway from my country region (Sri Lanka) which is more cheaper. They have provided me the api details. I just want to know where to place the code in the website to send the sms

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