All of the newer cards have the micro card inserted. If it does not have that, then it is an older card, determined by what is printed on the label. I have never heard of any way to transfer the data on a standard SD to a micro. The Navionics card information is copyrighted data and cannot be copied and would not be legal to do so.
If it happens to be a much older card, the data will obviously be old also and out of date.
IF that is the case then I would just suggest you call one of the board sponsors and get a new card...OR...THE good news! Use that card as the key to the Navionics+ update card for $99. His new card will not be a Platinum card but your money will not have been wasted since by using that card and the $99 update...you can get a new regular priced $199 Nav +, and you are about even. AND, that new Nav+ will have the most updated data...free updates for one year. Navionics does about 2000 updates a day so he will always be current anytime he wants. Note you must register that card when you get it within 60 days (free) at Navionics.com to be able to get the free year of updates. At the end of the year, if he likes and wants to continue the daily update subscription, just resubscribe for $99 and good to go...If he does not, then the card stays exactly as it was on his last update and he can keep it as it is at no further cost.
One thing you should realize is that the Platinum + card and the Hotmaps Platinum card are two different cards for different purposes. Depending on location, available to you to research on Navionics.Com, I would highly suggest you make sure you are buying the correct card. Once opened they cannot be returned. The Platinum cards are regional so make sure to check that out before you buy. The Navionics+ card is good for all of the US and Canada. The Brand NEW Regional Navionics+ card is only $149 and is REGIONAL (same regions defined on the Hotmaps Platinum cards) but with the same features and benefits of the full USA card...but just for a region at a reduced price.
Hope that helps a little, If not, lots of guys here with good info and we all can clarify further if you need.
Tommy
Prostaff Lowrance/Navico
Prostaff Marine Specialist/Navionics