Researching I find that solar collectors are connected with a mix of serial and parallel but I cannot find an explanation as to how to figure out how to do what.

I'm no solar expert but I have a tiny bit of ancient forgotten knowledge.

series
-3v+ -3v+ = 6v between the ends

I don't think you can mix watts or volts in a string without the higher watt(or volt) modules dropping to a matching current(or volts), matching the lower watt modules. Another-words all modules will match the smallest watts or volts in the string.
Not positive what you have, but think thats what you will see in a series sting.
Thinking of each one somewhat like a flashlight battery might be more familiar to you.

Parallel increases the current, or watts.

That size reminds me of every 12 volt car battery 'keeper upper' I've ever seen. They output about 100ma in full sun and about 15 volts. When you put them on your
13.4 volt car battery they still output about 100ma and actually that just overcomes the degredation a car battery experiences. So they work.

I would measure the output in full sunlight. Use any voltmeter and see that it's 15 volts. If it's less then
that size will still output the wattage equal of 15 x 100 ma or 1500 mwatts = 1.5 watts. I won't do the math
for 3 volts or 6. But each cell in the device puts out about 1.2 volts or 1.5 volts and they are put in series or parallel or both to make a complete product. What you have is unknown until you measure it. But I'll guess what I said above.

They won't run much. 1.5 watts won't run much of a motor pumping water. If you get a dribble I'd be suprised. The best thing to do to make them work to the best effect is to

1. measure the voltages of each in full sun
2. see what voltage the pump requires.
3. match the cells to the pump voltage. That will
tell you if you can connect them directly or if you have
to put them in series to increase the voltage. If you put
a 12 volt one on a 4 volt motor there's so little energy the motor nor the cell will be damaged. You can short
the cells and they won't be damaged.

Obviously there's no way, nor reason, to reduce the voltage of the cell.. there is but it requires a circuit to
switch the voltage at 20,000 hz or higher up or down.
It's beyond what I would take my time to do.

Lastly to measure the current output you'll use an ammeter. Your voltmeter has that setting. That cell will not output more than 100 to 400 ma. Less than 1/2 amp in full sunlight. To be safe set the meter on the highest setting , even 10Amp setting and measure it. Then reduce the setting as you put the meter, set on amps, across the cell in full sunlight. You can also vary the sunlight on the cell if you perceive that the meter is
overloaded. 1/2 the cell covered is 1/2 the current.

Well that's the $1.00 tour. Enjoy and why not let us know what you ended up with.

Andre