As you might expect, this a common problem with sewing machine users, but there a lots of places online where you can access a manual for your Janome Memory Craft 3000. The first place to try would be content.janome.com, where you can download a PDF of the manual from Janome themselves.
If something goes wrong there, there are several other sites providing a similar service, such as :
Alternatively, you could try your luck in one of the sewing machine user community forums:
These sites offer advice not only on missing manuals, but repairs, spare parts, and general discussion on machine sewing.
Lastly, you can call the Janome customer support line on 1-800-631-0183, ext. 774, send them an email via their website or write to Janome at Janome America, 10 Industrial Avenue, Ste. 2, Mahwah, New Jersey 07430.
You could even upgrade from a Memory Craft 3000 to a newer model. Here's a YouTube user's review of the Janome 9000: