How should µeV be written out? Is it microelectronvolts? or microelectron-volts?
The Guide for the Use of the International System of Units (SI) from NIST on https://physics.nist.gov/cuu/pdf/sp811.pdf is useful for this.
In section 6.2.8 a relevant example is presented:
Examples of the use of prefix symbols with eV and u are 80 MeV (80 megaelectronvolts) and 15 nu (15 nanounified atomic mass units).