11mcd sounds like a mistake. 11,000mcd maybe. mcd stands for milli-candellas, which is a unit of luminous intensity. In other words, how intense is the light in the direction in which it is brightest. That's different from total light output, which is measured in Lumens. Two leds might output the same total amount of light (lumens) but one might have a much higher intensity than the other because it puts out its light in a much narrower beam, whereas the other has a much wider viewing angle.
For your turn lights, I think brightness is important. To get the most brightness, you need to supply the maximum current you can to the leds, and minimise the multiplexing ratio.
Your leds have a max continuous current of 20mA, but as INTP says, you can often exceed that limit if you are multiplexing, because the current will not be continuous. Question is, by how much can you exceed it. Even top quality leds from big name manufacturers only give very brief information on this in their data sheets. For example, the max pulsed current might be 100mA, but the pulses have to be no longer than 0.1ms with a 10ms delay between pulses.
But for less expensive, brand-X leds, no such information is available and you exceed the max current at your own risk.
With your 5x10 matrix, you can multiplex either by row (giving a 1 in 5 multiplex ratio) or by column (givng a 1 in 10 ratio). If you can't safely exceed 20mA, it would be better/brighter to go with multiplexing by row.
This would mean up to 10 leds lit at once, a total of 10 x 20mA = 200mA. This is the limit of what the Uno's chip can source or sink. Even so, you have to be careful to spread the current between ports so that no port exceeds 100mA.
Switching the rows will require transistors or a driver chip, because the Uno's pins cannot deal with 200mA. As your rows are common cathodes, I would recommend 5 x bc337 transistors as low-side switches.
Your led series resistors would be on the columns, so 10 of them. Ideally, value should be (5.00 - 2.25) / 0.020 = 137R, so go for next highest available value 150R.
You also need 5 resistors on the bases of the transistors. Assuming gain of 50, they should be 5 / (0.2 / 50) = 1.25K, so 1K should be OK.