Complete instruction in algebra, book 1
The Euler Archive retains a PDF of a 1920 German edition, as well as an 1822 English translation.
An 1807 French translation, and an English-language audiobook, are both available at Archive.org.
Original Source Citation
St. Petersburg: Imperial Academy of Sciences, Volume 1, pp. 1-356.
Opera Omnia Citation
Series 1, Volume 1, pp.1-208.