Capacitors will have a number on them like 103, 104, 224 ... . The last number represents the number of zeroes. All values are in picofarads.
For example: 103 becomes 10 + 000 (3 zeroes) pF = 10000 pF = 10 nF
For example: 224 becomes 22 + 0000 (4 zeroes) pF = 220000 pF = 220 nF = .22 uF

A capacitor that has a decimal is typically measured in uF.
For example: .47 = .47 uF = 470 nF

The letter on a capacitor designates the tolerance.
J = +/- 5%
K = +/- 10%
M = +/- 20%

For example: .47K becomes .47 uF +/- 10% of .47 uF. Therefore the measured value of the capacitor can be within the range of .423uF to .512uF.

The voltage listed on the capacitor is its operating voltage.
For example: a capacitor with 250V marked on it may be operated at any voltage up to, but not exceeding 250V. If 250V is exceeded, the capacitor may not work properly. It is therefore possible to replace a 100V capacitor with a 250V capacitor if a 100V capacitor cannot be found. However, the 250V capacitor may be physically larger than the 100V capacitor, so it may no longer fit in the circuit with the other components.

Any other markings on the capacitor are probably lot or batch numbers, and are only used by the manufacturer.