In "Destiny 2," the process of acquiring the Khvostov 7G-02 auto rifle does not involve Motes of Light. Motes of Light were a currency in the original "Destiny" game used primarily for experience boosts and purchasing certain items from vendors. In "Destiny 2," currencies and materials have evolved, and they differ significantly from those in the original game.
To obtain the Khvostov 7G-02 in "Destiny 2," players typically engage in a specific quest that may involve collecting weapon parts or completing certain tasks, but this quest does not require Motes of Light. Instead, you might be asked to complete activities that yield other types of in-game rewards or currencies relevant to "Destiny 2's" current economy.
If you're seeking to acquire the Khvostov, check for any available quests related to legacy or nostalgic weapons, often available during special events or updates. These quests are typically outlined in the game's quest log once activated, providing step-by-step instructions on how to proceed without the need for Motes of Light.