Here for the Jensen remote just click below;

Here is link to the manual:

http://www.remotecodelist.com/remotes/jensen/JR300C.pdf
Sorry the manual was not the correct one for this remote. I thought it would provide simular codes to your product.
Here is some helpful information I found:
Without the code on JER-323:
1.Manually turn on the component you want the remote to control.
2. Press the device button, example:( TV) and the (power button) for 3 seconds until the (on/off button stays lit).
3. Once the (on/off) button is lit, press the (on/off) button until the unit (the TV or unit you are trying to control.) turns off.
4. When the code is located, press the (stop) button at the bottom to save the code.
Here are some codes I found for the Jensen 323:
GE VCR: 2000, 2013, 2021, 2022, 2053, 2087, 2089, 2091, 2115, 2120
Motorola Cable Box: 5000, 5003, 5046, 5047, 5052
Mitsubishi TV 0093, 0150, 0178, 0019
JVC VCR 0067, 0041, 0008
JVC DVD 0558, 0623

Hope it help you;

Regards,
VOTIT