Your best hope is this page: https://www.janome.com/siteassets/support/software-files/windows-10-upgrade-sentinel-run-time-environ-h0033.pdf
That's assuming that you are using Windows 10. If it doesn't work, you are pretty much out of luck.

For onlookers, this is one of the problems with software in general. The software publisher only wants people who have paid for the software to be able to use it. Likewise, when you buy software you assume that you'll be able to use it as long as you want. There are lots of wild cards though. Computers change frequently. The operating systems that make them work change even faster. Protecting software from piracy requires a lot of very specialized code, and much of it is deeply linked to the operating system. When Windows changes, this software needs to change as well. Usually the publisher of the software will release an update. But these updates are not forever. In the case of the original Janome Digitizer (which includes Digitizer Jr), the seller, Janome, has decided to abandon it. The publisher, Wilcom, is no longer interested in improving it, since their customer (Janome) has dropped it. In the ever-changing world of technology this happens over and over. Consider, for example, all the software that was once sold on floppy disk. CDs and DVDs are also on the way out. The only way to keep from being left with orphaned software is to keep the same computer forever, and never update it. Virtual machines allow this, at least until the virtual machine software stops supporting the version of virtual machine that you have.