There's all sorts of pin outs. Some actually have the schematic symbol and CW, CCW written on them.
There is a 3-lead patteren like:
x---x
--x--
Adj
and
--x--
x---x
Adj
This would be a side adjust pot. The center pin is the wiper. It's sometimes suggested that you add a pin
--x--
x-x-x
So, it can accomodate both types of pots.
If you are using the trimmer in a 2 wire mode, it's SUGGESTED that one end be tied to the wiper. Failures occur at the end point, and that connection makes it more reliable
103 is 10K and 104 is 100K; It's not a part number or a type number.
You can use your ohmmeter to determine which is the wiper. You can also attach wire feet if you have to accomodate somehting that won't fit the breadboard.
Multi-turn pots click at the end, so if you know it's a 10 turn, move it to the CCW end and move 3 turns CW.
Say you had a 1K pot. You would have a 0 point, one about 300 and one at 1K. You can now identify the pot.
You can also find the datasheet for your particular potentiometer.
It is most common to have the wiper on the center pin. So far I've not seen one deviate from that but I don't know all.
The numbers on the pot describe their resistance range. 103 means 10 followed by 3 zeros. In other words, 10,000Ω (or 10KΩ) 104 would be 10 followed by 4 zeros. IOW: 10,0000 (or 100,000Ω or 100KΩ).
The resistance of the pot is from end to end. The wiper selects variable points along that resistance. So you get 10K¸ from (lets call them) pins 1 & 3. Pin 2 (the center pin) is the wiper, and depending on where it is located gives you the variable or adjustable trim to the resistance.
Some applications may include the upper limit and the lower limit with the wiper selecting a position somewhere in between, settable by the user. Other applications may just simply be a variable resistance where pins 1 & 2 are tied together and you set your resistance between those two pins and pin 3.
If you'd like a drawing I'd be happy to accommodate you. Just ask. But you probably can find thousands of images on line.