Losing your 3ds Max serial number can be a frustrating experience, but there are steps you can take to recover it and get back to using the software. Here are some tips for recovering a lost 3ds Max serial number:

1. Check Your Email: If you purchased 3ds Max online, the serial number may have been sent to you via email. Search your inbox for any emails from Autodesk or the reseller you purchased the software from.

2. Check Your Account: If you have an Autodesk account, log in and check your purchase history. Your serial number should be listed there along with any other details about your purchase.

3. Contact Customer Support: If you are unable to find your serial number in your email or account, contact Autodesk customer support for assistance. They may be able to look up your purchase and provide you with the serial number.

4. Check the Software: If you have already installed 3ds Max on your computer, you may be able to find the serial number within the software itself. Open 3ds Max and navigate to the Help menu, then select About Autodesk 3ds Max. Your serial number may be listed there.

5. Check Your Receipt: If you purchased 3ds Max from a physical store, check your receipt for the serial number. It may be printed on the receipt along with other details about your purchase.

6. Register Your Product: If you have not already done so, register your product with Autodesk. This can help you keep track of your serial number and other important information in the future.

Losing your 3ds Max serial number can be a hassle, but with these tips, you should be able to recover it and continue using the software without any issues. Remember to keep your serial number in a safe place in case you need it again in the future.