The first anime series (1997) covers Black Swordsman arc (volume 1-3) until just before the end of Golden Age arc (volume 3-13). However, it includes original episodes and some modifications to the original story. (Source: Yahoo! Chiebukuro (Japanese))
The OVA (or 3-part movies) covers the whole Golden Age arc, which is volume 3-14, hence the name Berserk: The Golden Age Arc.
The second anime series (2016) covers the beginning of Black Swordsman arc (chapter 1&2), omits the whole Golden Age arc, then continues on Conviction arc (volume 14/chapter 115 - volume 21) until Falcon of the Millenium Empire arc (volume 22~)
The third anime series, Berserk: The Golden Age Arc - Memorial Edition is based on the remastered version of the OVA, edited for TV broadcast, and added new scenes. It also covers the whole Golden Age arc.
For additional reference, the manga is still on-going (volume 39) as of now. The story arcs:
- Black Swordsman: Volume 1-3
- Golden Age: Volume 3-14
- Conviction: Volume 14-21
- Falcon of the Millennium Empire: Volume 22-35
- Phantom World (Fantasia): Volume 35~