I have a couple of quilting patterns that have measurements of 3/8", 7/8", 5/8" and 1/8". Where would you find these on a ruler? Or how would you change them to a decimal point on a ruler that's easier to measure like.25 or.50? Hope that makes sense?

Here is an on-line conversion site.
Online Conversion - Common Length Conversions (http://www.onlineconversion.com/length_common.htm)

To change from a fraction to a decimal:

Divide 1 by the denominator, multiply by the nominator.

3/8 is equal to 0.375

1 divided by 8 is 0.125
0.125 multiplied by 3 is 0.375

Which is just another way of saying divide the numerator by the denominator.

You can purchase a measuring tape with the fractions marked like this.

https://www.askmehelpdesk.com/members/hkstroud-albums-+pictures-picture527-tape-measure.jpg

Thanks.