Naming alkyl groups of an ester
You are going about naming them incorrectly, try breaking it into two parts: the conjugate base of a carboxylic acid and an alkyl group.

$\hspace{5.9cm}$

Combining the two, we get:

$\hspace{6.9cm}$

Both the carboxyl and alkyl carbon chains can be numbered, with the carboxyl chain starting at the carboxyl carbon, and the alkyl chain starting at the carbon that places its bond to the ester oxygen at the lowest position. See below:

$\hspace{5.5cm}$

To refer to a specific carbon, simply say "at position $x$ on the carboxyl/alkyl chain."