Hi Archana,
It's important to respect the intellectual property rights of others when using images or any other copyrighted material. Simply giving a reference or credit may not be sufficient to comply with copyright law.
In the case of course materials on Udemy, the course creator usually holds the rights to the content they provide. If you haven't received a response from the course creator regarding your request to use their images, it's best to refrain from using them until you obtain explicit permission. Creating your own drawings or finding alternative images that are properly licensed for your study purposes would be a safer approach.
If you require specific images from the course material, you might want to reach out to Udemy's support team for guidance on how to handle this situation. They can provide you with more information on the terms and conditions of using course materials and may be able to assist you in contacting the course creator.
Remember, it's always best to obtain permission or use content that is explicitly licensed for the purpose you intend to use it for to avoid any potential legal issues.