Learn Farsi: آیا این دومین سالگرد شرکت شما است؟ - Is this the second anniversary of your company?

Ordinal numbers ending in -omin (like dovvomin, meaning second) are placed directly before the noun they describe, and they do not take an ezafe. You simply say dovvomin salgard side-by-side.

Could I use dovvom instead of dovvomin in this sentence?

Yes, but the word order would have to change! If you use the Type 1 ordinal (dovvom), it acts like a regular adjective. It goes after the noun and requires an ezafe, becoming salgard-e dovvom. Using dovvomin before the noun is often preferred for emphasis or in slightly more formal contexts.

How do you break down the word salgard (anniversary)?

It is a compound word made of sal (year) and gard (from the verb root for turning or returning). So it literally translates to the turning of the year.

Why is there an ezafe between sherkat and shoma?

Because this is a possessive construction. While dovvomin doesn't use an ezafe because of its special pre-noun placement, sherkat (company) must connect to shoma (you) to mean your company. Therefore, it becomes sherkat-e shoma.