We currently have Windows version 2003 or there about's, if we purchase the latest version for the Mac, can all that data from that old version be brought into the new version?
Not exactly...it depends on what data you have and want to bring over...QWin and QMac are quite different. More on that below. But the path to get there would most likely be upgrading to QWin 2004, then upgrading to at least QWin 2013, both of which are available for free from Quicken here, then migrating over to QMac.
If you decide to migrate your data, you do need to convert. Since your data is from before QW2010, follow the following; here is the entire process:
NOTE: Be aware that at this time, it is very difficult to convert back from Mac to Windows, as there are many problems with the reverse conversion process.
I also suggest that you make sure that Quicken for Mac subscription will meet your needs, since it was re-written from the ground up (first with Quicken Essentials in 2010, then again with QM2015 onward) and is not the same product as the Windows version, so there are some features that are still not there e.g. full loan amortization*, 2-line display, QuickMath, or are not as fully developed yet, e.g. Customized Reports, some investment performance reports and stats (therefore some data may not carry over). You can start here:
*NOTE: Support for fixed rate loans has been released as of QM2017 v4.5.x but there is no announced timing for support for variable rate or simple daily interest loans.
You will also want to look at a more detailed comparison done by a SuperUser which also identifies nuances not mentioned elsewhere (and read on for comments from other users too on that same discussion thread):
Note that there are many differences that are rather subtle, that are not necessarily identifiable via documentation, for example, the 12-month budget feature does not allow including transfers, including investment income, selecting specific accounts, or have rollover capability.
If you find that QMac subscription does not meet your needs, the alternative is to run Quicken for Windows in a virtual machine on your Mac. There are 5 popular products you can use: Parallels, VMWare Fusion, Oracle VirtualBox, Bootcamp or CrossOver. The first 4 require you to also buy a copy of Windows. The first 2 cost $50-80, the third and forth are free. CrossOver also costs about $50-$80 but does NOT require you to buy Windows.
If you plan to keep your PC & Mac, you could also run Quicken on the PC and use remote access (several free options, e.g. NoMachine and Teamviewer) to access Quicken from your Mac (or even a tablet or phone) (see this great article for complete review of many options (most are free): http://machow2.com/rdp-for-mac/ ).