Preparing for Starship Combat
Starship combat is played on a grid of hexes with figures representing the starship combatants. Starfinder Flip-Mat: Basic Starfield and the starship pawns in Starfinder Core Rulebook Pawn Collection make perfect accessories for this portion of the game.
The hexes don’t represent a specific distance, as Starfinder’s portrayal of movement and combat in three-dimensional space is more fluid and narrative than realistic. Unless otherwise specified, each ship occupies 1 hex, regardless of its size.
Source
Core Rulebook pg. 316