1. convert .621 hl to liters?

2. Convert .013 dl to liters?

3. Convert .00078 mg to kg?

4. Convert 2.45 g to cg?

5. convert 1.9 km to cm?

6. convert .0476 mm to dam?

7. Convert 6.4 ul to nl?

Do them all this way:
(a) figure out what the units mean. For exampple, "ul" is microliters (10^-6 l) and "nl" is nanoliters (10^-9 l)
(b) Write down the conversion factor that can be multiplied by the original first number (like 6.4 ul) to get the converted number in the new units. There are 1000 nanoliters in a microliter.

(c) Then perform the multiplication to get the new quantiy in new unitws. This is called the "factor label" method.

Here are some examples:
3. 7.8*10^-4 mg * (10^-6 kg/mg) = 7.8*10^-10 kg
7 6.4 ul * (1000 nl/ul) = 6400 nl

Try the others yourself. You will need to familiarize yourself with the SI prefixes like hecta- and deci- and centi- etc
You will find them here:
http://www.physics.nist.gov/cuu/Units/prefixes.html

1. To convert .621 hl to liters:

(a) "hl" stands for hectoliters, which is equal to 100 liters.
(b) The conversion factor is 1 hl = 100 liters.
(c) Multiply .621 hl by the conversion factor: 0.621 hl * 100 liters/hl = 62.1 liters.

2. To convert .013 dl to liters:

(a) "dl" stands for deciliters, which is equal to 0.1 liters.
(b) The conversion factor is 1 dl = 0.1 liters.
(c) Multiply .013 dl by the conversion factor: 0.013 dl * 0.1 liters/dl = 0.0013 liters.

3. To convert .00078 mg to kg:

(a) "mg" stands for milligrams, which is equal to 0.000001 kilograms.
(b) The conversion factor is 1 mg = 0.000001 kg.
(c) Multiply .00078 mg by the conversion factor: 0.00078 mg * 0.000001 kg/mg = 0.00000000078 kg.

4. To convert 2.45 g to cg:

(a) "g" stands for grams, which is equal to 100 centigrams.
(b) The conversion factor is 1 g = 100 cg.
(c) Multiply 2.45 g by the conversion factor: 2.45 g * 100 cg/g = 245 cg.

5. To convert 1.9 km to cm:

(a) "km" stands for kilometers, which is equal to 100,000 centimeters.
(b) The conversion factor is 1 km = 100,000 cm.
(c) Multiply 1.9 km by the conversion factor: 1.9 km * 100,000 cm/km = 190,000 cm.

6. To convert .0476 mm to dam:

(a) "mm" stands for millimeters, which is equal to 0.0001 decameters.
(b) The conversion factor is 1 mm = 0.0001 dam.
(c) Multiply .0476 mm by the conversion factor: 0.0476 mm * 0.0001 dam/mm = 0.00000476 dam.

7. To convert 6.4 ul to nl:

(a) "ul" stands for microliters, which is equal to 0.001 nanoliters.
(b) The conversion factor is 1 ul = 0.001 nl.
(c) Multiply 6.4 ul by the conversion factor: 6.4 ul * 0.001 nl/ul = 0.0064 nl.

By following these steps and using the appropriate conversion factors, you can convert between different units of measurement. The provided link contains a helpful resource for familiarizing yourself with SI prefixes and their corresponding values.