With some clarification, maybe I can help, even if only a little...
Our
Furuno chartplotter system is NAVNet3D (NN3D), embodied in a 12" Multi-Function Device (MFD). The
charts reside in memory, not on a removable chip (SD card). The SD card is an easy way to transfer downloaded
charts from high-speed home computer (for example) to the MFD.
The
software in there is NOT actually exactly
MaxSea TimeZero; more like a very similar, near mirror of TimeZero. TZ is the computer (e.g., laptop) implementation.
IF you mean you have an NN3D (or newer) MFD, then the next useful bit of info is version number. When you turn the thing on it'll show you that number; I think our NN3D is 2.something-or-other... but you may have that or something newer (TZ Touch, whatever). Version number might not be all that important (at least at first) if the system is working properly.
The third useful thing to specify is your cruising location. Wherever, I think you can just download the charts. Charts are available for download, here, if that works for where you are: https://www.furunousa.com/en/products/gps_and_chart_plotters/browse?filter=Discontinued.eq.false&group={CFBDF65 2-0102-4A61-9835-CF99FD2D0A6F}&groupName=Charts for
NavNet 3D, TZtouch & TZtouch2
If it happens to be in the
USA and if the stars and moon align with all that MFD/version stuff... NOAA charts, both raster and vector formats, are free.
C-Map and
Navionics charts are $$$. I dunno much about charts for elsewhere...
There's a MapMedia site somewhere, but I don't have the bookmark handy just now; MapMedia are the guys who actually make the Furuno and TZ charts; same charts
work for both MFD and
laptop implementations, although there are some differences in the way TZ works with ZIP files (it does) versus MFD (does not). Minor detail...
-Chris