A muonium consists of a positive muon associated with an orbital electron, and the spontaneous conversion to antimuonium serves as a clear indication of new physics beyond the Standard Model in particle physics.One of the most important aspects in muonium-to-antimuonium conversion experiment (MACE) is to increase the muonium yield in vacuum to challenge the latest limit obtained in 1999. This study focuses on a simulation of the muonium formation and diffusion in the perforated silica aerogel. The independent simulation results can be well validated by experimental data. By optimizing the target geometry, we find a maximum muonium emission efficiency of 7.92(2)% and a maximum vacuum yield of 1.134(2)% with a typical surface muon beam, indicating a 2.6 times and a 2.1 times enhancement, respectively. Our results will pave the way for muonium experiments.