Locating a paper in Euler's complete works

I'm currently reading Disquisitiones Arithmeticae and I keep seeing references to Euler such as "Comm. acad. Petrop., 8 [1736], 1741, 141". My question: How can I go about locating this paper in http://eulerarchive.maa.org/ ? (Note: I want to know how to do it myself so an explanation would help - thanks!)

I imagine that Petrop. is short for Petropolis, literally, the city of Peter, so, presumably St. Petersburg. In the archive, the first section of the search by publication is "St. Petersburg Academy Publications", and the first publication is called Commentarii. That fits "Comm. acad. Petrop."; the table of contents for volume 8 (1736, published 1741) lists a few papers by Euler, one on page 141, all of which fits the citation.

(The table of contents actually gives the author of the paper starting on page 141 as Eiusdem; this means "of the same person" in Latin, similar to ibidem in modern bibliographies. You might be able to guess this from context.)

I would start by looking at the dates - this was published in 1741, on page 141 of Comm. Acad. Petrop., 8.

A quick perusal yields E54 -- Theorematum quorundam ad numeros primos spectantium demonstratio